Lightweight fragmentation and reliability for fixed mobile convergence access stratum and non-access stratum signaling

ABSTRACT

A method is provided to implement a fragmentation mechanism for a session between a 5G-RG and access gateway function (AGF) communicating over point to point protocol over Ethernet (PPPoE) that encapsulates control messages, where the 5G-RG or the AGF is a sender of a message. The method includes receiving the message to be sent that does not fit within a maximum transmission unit for the session, generating a first fragment of the message and a second fragment of the message, and sending the first fragment of the message and the second fragment of the message to a receiver, the second fragment including metadata with a length, and cyclic redundancy check.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is claims the benefit of U.S. Provisional ApplicationNo. 62/937,217, filed Nov. 18, 2019, which is hereby incorporated byreference.

TECHNICAL FIELD

Embodiments of the invention relate to the field of fixed mobileconvergence; and more specifically, to a process for managingfragmentation related to access stratum and non-access stratumsignaling.

BACKGROUND ART

5G provides a new avenue for providing fixed access to broadband in aresidential context. This utilization of 5G is referred to as fixedmobile convergence. In this context, residential broadband served by a5G System can be provided to any number of user devices including mobilehandsets, computers, tablets, and other computing devices that connectto a residential gateway or similar customer premise equipment. Theresidential gateway then may connect with the 5G network via wirelineaccess facilities such as a passive optical network (PON) or digitalsubscriber line (DSL) in addition to the possibility of fixed wirelessaccess (FWA) and combinations of these access technologies.

The deployment of 5G wireline access typically will involve anintervening Ethernet based legacy access network often based upon theBroadband Forum TR-101 and related specifications. This will be for thepurposes of meeting wholesale or regulatory requirements and differsfrom the radio architecture where traffic is adapted onto 5G at a radiobase station of a cellular network with no intervening network.Converged 5G wireline access to the 5G System carries user data between5G residential gateways (5G-RG) and a 5G Access Gateway Function (i.e.,a fixed network (F)-AGF) across deployed access networks. The transportencapsulation used between the 5G-RG and the F-AGF needs to meet avariety of requirements including the ability to transport both accessstratum (AS) and non-access stratum (NAS) control traffic within avirtual local area network (VLAN) identified point to point (p2p)logical circuit between a 5G-RG and an F-AGF. Life cycle management ofPDU sessions is performed via 5G control plane interactions between theuser equipment (in the wireline case at a 5G-RG) and the 5G Core.

Point to point protocol (PPP) over Ethernet (PPPoE) is a protocolcommonly used in wireline networks and has been deployed for some 20years. PPPoE provides mechanisms for session multiplexing and employs ahierarchy of protocols (link control protocol (LCP), network controlprotocol (NCP) and similar protocols.) to perform session lifecyclemanagement via user plane transactions. PPPoE is typically transportedover a provisioned and VLAN delineated access circuit. PPPoE has beenselected as the preferred transport for 5G control traffic between a5G-RG and an F-AGF. The PPP suite of protocols includes a vendorspecific network protocol (VSNP), which the Broadband Forum has selectedas the underlying encapsulation for NAS and AS traffic.

The VSNP, PPP, PPPoE stack imposes a small amount of protocol overheadwhich reduces the maximum transmission unit (MTU) for a single VNSPprotocol data unit (PDU) to a value slightly less that the Ethernet 1500byte MTU. The exact amount is indeterminate at the time of writing dueto incomplete design work in standardization. NAS and AS traffic arecarried over the VNSP. A NAS message may not have a theoretical lengthrestriction. As a practical matter, a NAS message can be restricted byradio resource control (RRC) used as a transport over radio interfaceswhich has an MTU of 8188 bytes. Thus, NAS messages create a problem withcompatibility with VSNP and PPPoE as a simple encapsulation due to thepotential for NAS messages to be longer than the available MTU.

SUMMARY

In one embodiment, a method is provided to implement a fragmentationmechanism for a session between a 5G-RG and access gateway function(AGF) communicating over point to point protocol over Ethernet (PPPoE)that encapsulates control messages, where the 5G-RG or the AGF is asender of a message. The method includes receiving the message to besent that does not fit within a maximum transmission unit for thesession, generating a first fragment of the message and a secondfragment of the message, and sending the first fragment of the messageand the second fragment of the message to a receiver, the secondfragment including metadata containing a message length, and a cyclicredundancy check.

In another embodiment, a method is provided to implement a fragmentationmechanism for a session between a 5G-RG and AGF communicating over PPPoEthat encapsulates control message, where the 5G-RG or the AGF is areceiver of a message. The method includes receiving a first fragmentand a second fragment of the message from a sender, determining whetherthe second fragment is an end fragment, the end fragment includingmetadata containing a message length, and cyclic redundancy check,checking the message number, checking the metadata length against thefirst fragment and second fragment, validating the cyclic redundancycheck, and extracting the message from the first fragment and secondfragment, in response to the message length, and cyclic redundancy checkbeing correct.

In one embodiment, a computing device can implement a method of afragmentation mechanism for a session between a 5G-RG and AGFcommunicating over PPPoE that encapsulates control messages, where the5G-RG or the AGF is a sender of a message. The computing device includesa non-transitory machine readable medium having stored therein thefragmentation mechanism, and a processor coupled to the non-transitorymachine readable medium. The processor can execute the fragmentationmechanism. The fragmentation mechanism can receive the message to besent that does not fit within a maximum transmission unit for thesession, generate a first fragment of the message and a second fragmentof the message, and send the first fragment of the message and thesecond fragment of the message to a receiver, the second fragmentincluding a length of the message, and a cyclic redundancy check.

In a further embodiment, a computing device can implement a method of afragmentation mechanism for a session between a 5G-RG and AGFcommunicating over PPPoE that encapsulates control messages, where the5G-RG or the AGF is a receiver of a message. The computing deviceincludes a non-transitory machine readable medium having stored thereinthe fragmentation mechanism, and a processor coupled to thenon-transitory machine readable medium. The processor can execute thefragmentation mechanism. The fragmentation mechanism can receive a firstfragment and a second fragment of the message from a sender, determinewhether the second fragment is an end fragment, the end fragmentincluding metadata containing a message length, and a cyclic redundancycheck, check the message number, check the message length against thefirst fragment and second fragment, validate the cyclic redundancycheck, and extract the message from the first fragment and secondfragment, in response to the message number, and cyclic redundancy checkbeing correct.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 is a diagram of one embodiment of a network implementing fixedmobile convergence.

FIG. 2 is a diagram of one example illustration of the communicationmodel between the 5G-RG and the AGF incorporating a fragmentationmanagement mechanism.

FIG. 3A is a diagram of one embodiment of a message fragmentationformat.

FIG. 3B is a diagram of another embodiment of a message fragmentationformat.

FIG. 3C is a diagram of a further embodiment of a lighter messagefragmentation format.

FIG. 4A is a flowchart of one embodiment of the sender finite statemachine for implementing the fragmentation mechanism.

FIG. 4B is a flowchart of one embodiment of another sender finite statemachine for implementing a lighter fragmentation mechanism.

FIG. 5A is a flowchart of one embodiment of the receiver finite statemachine for implementing the fragment mechanism.

FIG. 5B is a flowchart of one embodiment of another receiver finitestate machine for implementing a lighter fragmentation mechanism.

FIG. 5C is a flowchart of one embodiment of a process of an accessgateway function (AGF) to support the lighter fragmentation mechanism.

FIGS. 6A-H are diagrams illustrating a set of cases for the operation ofthe fragmentation mechanism.

FIG. 7A illustrates connectivity between network devices (NDs) within anexemplary network, as well as three exemplary implementations of theNDs, according to some embodiments of the invention.

FIG. 7B illustrates an exemplary way to implement a special-purposenetwork device according to some embodiments of the invention.

FIG. 7C illustrates various exemplary ways in which virtual networkelements (VNEs) may be coupled according to some embodiments of theinvention.

FIG. 7D illustrates a network with a single network element (NE) on eachof the NDs, and within this straight forward approach contrasts atraditional distributed approach (commonly used by traditional routers)with a centralized approach for maintaining reachability and forwardinginformation (also called network control), according to some embodimentsof the invention.

FIG. 7E illustrates the simple case of where each of the NDs implementsa single NE, but a centralized control plane has abstracted multiple ofthe NEs in different NDs into (to represent) a single NE in one of thevirtual network(s), according to some embodiments of the invention.

FIG. 7F illustrates a case where multiple VNEs are implemented ondifferent NDs and are coupled to each other, and where a centralizedcontrol plane has abstracted these multiple VNEs such that they appearas a single VNE within one of the virtual networks, according to someembodiments of the invention.

FIG. 8 illustrates a general purpose control plane device withcentralized control plane (CCP) software 850), according to someembodiments of the invention.

DETAILED DESCRIPTION

The following description describes methods and apparatus for afragmentation management process to support access stratum (AS) andnon-access stratum (NAS) traffic over point to point protocol overEthernet (PPPoE) and vendor specific network protocol (VNSP) in a fixedmobile convergence (FMC) scenario between a 5G residential gateway(5G-RG) and an Access Gateway Function (AGF). In the followingdescription, numerous specific details such as logic implementations,opcodes, means to specify operands, resourcepartitioning/sharing/duplication implementations, types andinterrelationships of system components, and logicpartitioning/integration choices are set forth in order to provide amore thorough understanding of the present invention. It will beappreciated, however, by one skilled in the art that the invention maybe practiced without such specific details. In other instances, controlstructures, gate level circuits and full software instruction sequenceshave not been shown in detail in order not to obscure the invention.Those of ordinary skill in the art, with the included descriptions, willbe able to implement appropriate functionality without undueexperimentation.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Bracketed text and blocks with dashed borders (e.g., large dashes, smalldashes, dot-dash, and dots) may be used herein to illustrate optionaloperations that add additional features to embodiments of the invention.However, such notation should not be taken to mean that these are theonly options or optional operations, and/or that blocks with solidborders are not optional in certain embodiments of the invention.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other.

An electronic device stores and transmits (internally and/or with otherelectronic devices over a network) code (which is composed of softwareinstructions and which is sometimes referred to as computer program codeor a computer program) and/or data using machine-readable media (alsocalled computer-readable media), such as machine-readable storage media(e.g., magnetic disks, optical disks, solid state drives, read onlymemory (ROM), flash memory devices, phase change memory) andmachine-readable transmission media (also called a carrier) (e.g.,electrical, optical, radio, acoustical or other form of propagatedsignals—such as carrier waves, infrared signals). Thus, an electronicdevice (e.g., a computer) includes hardware and software, such as a setof one or more processors (e.g., wherein a processor is amicroprocessor, controller, microcontroller, central processing unit,digital signal processor, application specific integrated circuit, fieldprogrammable gate array, other electronic circuitry, a combination ofone or more of the preceding) coupled to one or more machine-readablestorage media to store code for execution on the set of processorsand/or to store data. For instance, an electronic device may includenon-volatile memory containing the code since the non-volatile memorycan persist code/data even when the electronic device is turned off(when power is removed), and while the electronic device is turned onthat part of the code that is to be executed by the processor(s) of thatelectronic device is typically copied from the slower non-volatilememory into volatile memory (e.g., dynamic random access memory (DRAM),static random access memory (SRAM)) of that electronic device. Typicalelectronic devices also include a set or one or more physical networkinterface(s) (NI(s)) to establish network connections (to transmitand/or receive code and/or data using propagating signals) with otherelectronic devices. For example, the set of physical NIs (or the set ofphysical NI(s) in combination with the set of processors executing code)may perform any formatting, coding, or translating to allow theelectronic device to send and receive data whether over a wired and/or awireless connection. In some embodiments, a physical NI may compriseradio circuitry capable of receiving data from other electronic devicesover a wireless connection and/or sending data out to other devices viaa wireless connection. This radio circuitry may include transmitter(s),receiver(s), and/or transceiver(s) suitable for radiofrequencycommunication. The radio circuitry may convert digital data into a radiosignal having the appropriate parameters (e.g., frequency, timing,channel, bandwidth, etc.). The radio signal may then be transmitted viaantennas to the appropriate recipient(s). In some embodiments, the setof physical NI(s) may comprise network interface controller(s) (NICs),also known as a network interface card, network adapter, or local areanetwork (LAN) adapter. The NIC(s) may facilitate in connecting theelectronic device to other electronic devices allowing them tocommunicate via wire through plugging in a cable to a physical portconnected to a NIC. One or more parts of an embodiment of the inventionmay be implemented using different combinations of software, firmware,and/or hardware.

A network device (ND) is an electronic device that communicativelyinterconnects other electronic devices on the network (e.g., othernetwork devices, end-user devices). Some network devices are “multipleservices network devices” that provide support for multiple networkingfunctions (e.g., routing, bridging, switching, Layer 2 aggregation,session border control, Quality of Service, and/or subscribermanagement), and/or provide support for multiple application services(e.g., data, voice, and video).

Overview

As part of providing wireline access to the 5G core for residences,deployed wireline networks carry user data and control traffic between5G residential gateways (5G-RG) and the 5G Access Gateway Function(AGF). The traffic between the 5G-RG and AGF is encapsulated to traversethe intermediate network devices along a data path. The encapsulationused between the 5G-RG and the AGF needs to meet a variety ofrequirements including being able to carry AS and NAS traffic over VNSPwhere a NAS or AS message may exceed the MTU of the 5G-RG-AGF interface.The embodiments provide a fragmentation management mechanism implementedat the 5G-RG and AGF to allow reliable fragmentation and reassembly ofAS and NAS traffic.

FIG. 1 is a diagram of one embodiment of a network implementing fixedmobile convergence including support for the fragmentation managementembodiments. A provider network 111, such as a converged 5G (“fifthgeneration”) wireline network provides broadband Internet access toresidences via a combination of cellular and wired technology. In oneembodiment, the provider network 111 carries user data and controltraffic between 5G-RGs the 5G AGF across both wired and wirelessconnections (e.g., over deployed TR-101 and TR 178 access networks).

A residential network consists of a set of user devices 101A-C connectedto the 5G-RG via wired and wireless access technologies (e.g., Ethernet,WiFi and similar technology). Any number of user devices 101A-C can beconnected to a 5G-RG 103. The 5G-RG 103 connects the residence to thefunctions of the provider network 111 and services of the wider Internetvia the 5G core (5GC) network 109. Communication within the residenceand between the user devices 101A-C and the 5G-RG 103 is based on localarea network technologies, in particular Ethernet. Communication betweensome classes or groups of home user devices and the 5G core may be viadifferent PDU sessions possibly supporting different network slices, andone of the roles of the 5G-RG is to map home user devices to theappropriate PDU sessions and vice versa.

Many of the functions of mapping access onto the 5G Core 109 areprovided by the AGF 107. The communication between the 5G-RG 103 and theAGF 107 utilizes a transport encapsulation for the control traffic thatperforms lifecycle management for PDU sessions that needs to meet avariety of requirements. The requirements of the transport encapsulationinclude the ability to manage NAS and AS traffic fragmentation within avirtual local area network (VLAN) identified point to point (p2p)logical circuit between the 5G-RG and the AGF. The transportencapsulation also must allow unmodified legacy equipment in the datapath (e.g., the legacy access node (AN) 105) to identify theencapsulation and snoop (i.e., access) specific fields in the payload.Some access nodes in the data path between the 5G-RG and the AGF (e.g.,Digital Subscriber Loop Access Multiplexers (DSLAMs) and optical lineterminators (OLTs)) currently inspect packets identified by specificEthertypes to identify protocols such as PPPoE, Internet Protocol (IP),address resolution protocol (ARP), and Internet Group ManagementProtocol (IGMP). The inspection of packets by the legacy network devicesmay be for the purpose of enhanced QoS management, policing ofidentifiers, and other applications. The operation of some providernetworks 111 are dependent upon this type of packet inspection. Thelegacy network devices are currently able to do packet inspection forPPPoE or IPoE packet encodings but would be unable to do so if a newtype of encapsulation, or an existing encapsulation using a newEthertype, were used.

The embodiments provide a fragmentation management mechanism that iscompatible with PPPoE that meets these requirements. The embodimentsalso take into consideration that fixed access is very sensitive to thecomplexity of residential gateways (e.g., the 5G-RGs), therefore, thefragmentation mechanism involves low overhead and does not negativelyimpact efficiency.

The embodiments support defining how NAS and AS information istransported between a 5G-RG and an AGF in the FMC architecture. Inparticular, the embodiments support the use of PPP/PPPoE as theunderlying network encapsulation and protocol. The embodiments utilize afinite state machine (FSM) on top of vendor specific network controlprotocol (VSNCP)/VSNP to transport NAS and AS protocol data units(PDUs). Using VSNCP/VSNP avoids requiring an IP stack for a P2Papplication, and the heavyweight state that IP reliability (transmissioncontrol protocol (TCP)/stream control transmission protocol (SCTP))brings to the table. Other equivalent protocols can also be utilizedwith VSNCP/VSNP being utilized herein by way of example and notlimitation.

The embodiments overcome problems of the prior art. The fragmentationmanagement process and system enables the handling of NAS traffic withrequirements that messages of significant length may occur. In theorythere is no maximum unit size for NAS, in practice the limit is imposedby SCTP/RRC which limits a NAS message to 8188 bytes. The signaling MTUnet of VSNP/PPP/PPPoE overhead may be approximately 1492 bytes. Thismeans the embodiments of a fragmentation mechanism will be needed forcompatibility. The embodiments are lightweight relative to thealternative of using an IP stack for fragmentation management. Theembodiments are scalable for NAS/AS at an AGF controller.

Without a fragmentation mechanism, the reliability requirements ofcontrol plane exchange would normally be left to the application layer.NAS traffic can normally be considered to be reliable as there aretimers, message retires and similar mechanisms at the NAS applicationlayer specified for the exchange of NAS messages between the 5G-RG andthe 5G System. AS messages would require similar application levelreliability mechanisms but over a different span; NAS traffic is betweenthe 5G_RG and the 5G Core, while AS traffic has a narrower scope ofcommunication with communication being between the AGF and the 5G-RG.The provision of a fragmentation mechanism changes the reliabilityrequirements as an application layer acknowledgement discipline cannothandle the new modes of failure introduced by the possibility of theloss of individual message fragments.

FIG. 2 is a diagram of one example illustration of the communicationmodel between the 5G-RG and the AGF incorporating a fragmentationmanagement mechanism. The model illustrates message encapsulation andthe 5G-RG-AGF stack. The control plane communication between the 5G-RG201 and the AGF 215 in an FMC network is encapsulated by PPP/PPPoE 203.The PPP/PPPoE 2103 encapsulates two streams including extensibleauthentication protocol for 5G (EAP-5G) 207 and VSNP 205. The EAP-5Gstream is utilized for session authentication. The VSNP 205 stream isutilized for transporting NAS (which is ciphered) and AS traffic, whereNAS is specified by 3GPP and AS will be specified by the BroadBand Forum(BBF). The fragmentation and reliability layer 221 supports theembodiments of the fragmentation mechanism process and system. Theillustrated scope of exchange relates to the control plane communicationbetween the 5G-RG 201 and the AGF 215. As shown, user planecommunication can be passed on IPv4 or IPv6, PPP, SFE, and Ethernet.

The 5G-RG 201 and AGF 215 implement FSMs to implement the fragmentationand reliability layer 221. The MTU between the 5G-RG and the AGF isknown. Intermediate nodes, e.g., access nodes (ANs), relay the PPP/PPPoEencapsulated traffic and are not affected by or have to directly supportthe fragmentation and reliability layer 221. The operation of thefragmentation mechanism process and system at the 5G-RG 201 and AGF 215is described further with relation to FIGS. 3, 4, and 5 where the 5G-RG201 and AGF 215 each implement a sender FSM and a receiver FSM for eachcontrol plane PPP/PPPoE session.

FIG. 3A is a diagram of one embodiment of a message fragmentationformat. The diagram illustrates that the fragmentation format can havefour message types a middle fragment, end fragment, acknowledgement(ACK), and negative acknowledgement (NAK). A message can be referred toas a service data unit (SDU) and the terms are used interchangeablyherein. The middle fragment type carries mainly a payload. The endfragment type includes SDU level metadata in the form of a length field(LEN) (e.g., an SDU length), message or SDU number (MSG #/SDU #), cyclicredundancy check (CRC), as well as payload. The metadata is located in afixed location at the start of an end fragment and provides sufficientinformation to validate successful receipt of all message/SDU fragmentsand reassembly of the message/SDU with all fragments in the correctorder. The acknowledgement and negative acknowledgement messages/SDUsalso include message/SDU numbers in order to disambiguate any raceconditions that might occur in protocol exchange. A long message/SDU isbroken up into multiple middle fragments and one end fragment. Amessage/SDU that fits in a single fragment is transmitted with a singleend fragment. If a message/SDU cannot fit into an end fragment with roomfor the overhead (i.e., the CRC, length, and message/SDU number), thenit is sent as two messages/SDUs, a middle fragment and an end fragment.

FIG. 3B is a diagram of another embodiment of a message fragmentationformat. The diagram illustrates that the alternate fragmentation formatcan have four message types a middle fragment, end fragment,acknowledgement (ACK), and negative acknowledgement (NAK). Thisembodiment provides further flexibility in fragment sizes. The middlefragment type carries mainly a payload. The end fragment type includes apayload as well as message/SDU level metadata. The message/SDU levelmetadata can include a cyclic redundancy check (CRC), message/SDU number(MSG #/SDU #), and a length field (LEN) (e.g., SDU length (SDU LEN). Themetadata is located at the end of an end fragment and providessufficient information to validate successful receipt of all message/SDUfragments and reassembly of the message/SDU with all fragments in thecorrect order. The fragment or SDU length information permits meta datato be located in an end fragment and ‘short’ middle fragments to beidentified. The acknowledgement and negative acknowledgement messagesalso include message or SDU numbers in order to disambiguate any raceconditions that might occur in protocol exchange. A long message isbroken up into multiple middle fragments and one end fragment. A messagethat fits in a single fragment is transmitted with a single endfragment. If a message cannot fit into an end fragment with room for theoverhead (i.e., the CRC, SDU LEN, and SDU number), then it is sent astwo messages, a middle fragment and an end fragment.

FIG. 3C is a diagram of a further embodiment of a lighter messagefragmentation format. This format is part of a process with lighterweight where the lighter fragmentation mechanism employs less messagingthan other embodiments. The lighter fragmentation mechanism reduces theoverhead by relying on an application layer acknowledgement disciplinefor reliability. In this embodiment, receiving a message that does notpass a reassembly test results in a message discard. NAS has timeoutsand acknowledgements that can handle duplicate detection. AS cantolerate duplicate information and is required to implement timeouts andacknowledgement messages (which were required for application layererror reporting independent of communication reliability). By reducingthe reliability process in the lighter fragmentation mechanism lessoverhead is required to manage acknowledgement and negativeacknowledgment information.

Returning to FIG. 3C, the diagram illustrates that the lighterfragmentation format can have two message types a middle fragment, andend fragment. This embodiment provides reduced overhead with fewermessage types and correspondingly reduced message exchange. The middlefragment type carries mainly a payload. The end fragment type includes apayload as well as message/SDU level metadata. The message/SDU levelmetadata can include a cyclic redundancy check (CRC), and a length field(LEN) (e.g., SDU length (SDN LEN). The metadata is located at thebeginning of an end fragment and provides sufficient information tovalidate successful receipt of all message/SDU fragments and reassemblyof the message/SDU with all fragments in the correct order. The endfragment can also include a payload portion. A long message is broken upinto multiple middle fragments and one end fragment. A message that fitsin a single fragment is transmitted with a single end fragment. If amessage cannot fit into an end fragment with room for the overhead(i.e., the CRC, and SDU LEN), then it is sent as two messages, a middlefragment and an end fragment.

The operations in the flow diagrams will be described with reference tothe exemplary embodiments of the other figures. However, it should beunderstood that the operations of the flow diagrams can be performed byembodiments of the invention other than those discussed with referenceto the other figures, and the embodiments of the invention discussedwith reference to these other figures can perform operations differentthan those discussed with reference to the flow diagrams.

FIG. 4A is a flowchart of one embodiment of the sender finite statemachine for implementing the fragment mechanism. The process of sendingNAS or AS data can be initiated in response to a NAS or AS message beingqueued for transmission at the sending node (i.e., either the 5G-RG orthe AFG) (Block 401). The start of the process can initialize a numberof retries that are permitted, e.g. 3 retries. In addition, the processcan initialize a tracking variable ‘remaining length to send’ to beequal to the message size or SDU length (Block 402). The processexamines the amount of data remaining to be sent to determine whetherthe fragment MTU is smaller or equal to the size of an end segmentpayload size, referred to as an end segment metadata length (ESML)(Block 403). If the data to be sent does not fit in an end segment, thenthe process prepares and queues middle fragments until the remainingdata fits in an end fragment to be sent to the receiver node (Block405). With each middle fragment sent, the remaining length to send isreduced by the size of the payload or fragment sent in the middlefragment (Block 406).

When the remaining data to be sent does fit within an end fragment, thenthe process prepares and queues an end fragment to be sent to thereceiving node (Block 407). As the end fragment is sent, the processstarts a timer and waits for an event (Block 409). If no event occursbefore the expiration of the timeout, then a check is made whether anumber of retries has been exhausted (Block 413). If the number ofretries has been exhausted, then the process returns an error (e.g., acommunication error). If the number of retries has not been exhausted,then the process checks the message size again (Block 403) to restart afragment retransmission (Block 405 and/or 407) and decrements the numberof remaining retries.

If a negative acknowledgement with the correct message/SDU number isreceived, then the timer is canceled (Block 411), a check of the numberof retries is made (Block 413) and either an error generated (Block 415)or a retransmission is started. Retransmission can entirely restart thetransmission of the data to be sent. If an acknowledgement with thecorrect message/SDU number is received, then the timer is canceled(Block 417) and the fragmentation and transmission process has completedsuccessfully (Block 419).

FIG. 4B is a flowchart of one embodiment of another sender finite statemachine for implementing a lighter fragmentation mechanism. This processof sending NAS or AS data can be initiated in response to a NAS or ASmessage being queued for transmission at the sending node (i.e., eitherthe 5G-RG or the AFG) (Block 401). The start of the process caninitialize a tracking variable ‘remaining length to send’ to be equal tothe message size or SDU length. The process examines the amount of dataremaining to be sent to determine whether the fragment MTU is smaller orequal to the size of an end segment payload size, referred to as an endsegment metadata length (ESML) (Block 453). If the data to be sent doesnot fit in an end segment, then the process prepares and queues middlefragments until the remaining data fits in an end fragment to be sent tothe receiver node (Block 457). With each middle fragment sent, theremaining length to send is reduced by the size of the payload orfragment sent in the middle fragment (Block 459).

When the remaining data to be sent does fit within an end fragment, thenthe process prepares and queues an end fragment to be sent to thereceiving node (Block 455).

FIG. 5A is a flowchart of one embodiment of the receiver finite statemachine for implementing the fragment mechanism. The process ofreceiving NAS or AS data can be initiated in response to receiving datafrom the sender. This received data can be stored in a buffer to beprocessed. In some embodiments, a buffer pointer is used that isinitialized to a starting point (e.g., setting the pointer to position0). The receiver awaits the receipt of fragments from the sender (Block503). When a middle fragment is received, the payload of the fragment isstored in the buffer and the buffer pointer is increased an amountequivalent to the length of the received fragment (Block 505). Theprocess then continues to await further fragments (Block 503).

When an end fragment is received, the buffer pointer is increased basedon the length of the fragment and the payload is stored in the buffer(Block 507). A check is then made to compare the message/SDU number ofthe received message with an expected message/SDU number (Block 509).The expected message/SDU number can be the next number in a sequence(with wrapping of the value known to those skilled in the art) or ifthis is the first message received since a receiver initialization, theexpected number will be marked as unknown and any received value will beaccepted, or if the sender and receiver have lost synchronization it canbe a value other than the last received message/SDU number, or the nextexpected message in the sequence. If the message/SDU number indicatesthat the message/SDU is a duplicate; indicated by the message/SDU numberbeing equal to the message number of the last message acknowledged, thenthe receiver sends an acknowledgement message including the metadatamessage/SDU number (Block 511) and the message is discarded. Any furtherduplicate messages that have been received, which are identified byduplicate message/SDU numbers, can be discarded after acknowledgement.The process then resets the buffer pointer and awaits a next message(Blocks 501 and 503).

If the message/SDU number in the metadata is the expected message/SDUnumber or an unexpected value (indicating the sender and receiver hadlost message synchronization) or the expected message/SDU number wasunknown, then the metadata message/SDU length is checked against thelength of data in the buffer (Block 513). If the length of the data inthe buffer is not greater than or equal to the message/SDU length of thereceived message, then a message fragment has been lost and the processsends a negative acknowledgement (NAK) with a message/SDU number (Block515). This causes the message to be discarded, the buffer reset, and theprocess to expect a retransmission of the message. If the message/SDUlength in the buffer is greater than or equal to the expectedmessage/SDU length, then the process computes the CRC over the messagein the buffer (e.g., the data in the buffer at the positions between thebuffer pointer and the buffer pointer minus the metadata message/SDUlength (Block 517)). If the CRC is not valid, it is assumed a fragmenthas been lost or out of order receipt has occurred, and a negativeacknowledgement with the message/SDU number is sent (Block 515). Thiscauses the message to be discarded, the buffer reset, and the process toexpect a retransmission of the message.

If the CRC is valid, then the message has been validated as beingreassembled correctly and an acknowledgement message is sent to thesender node (Block 519). The acknowledgement includes the message numberobtained from the message metadata. The last message/SDU number is thenset to the message/SDU number (Block 521). The message is extracted fromthe buffer and passed up the stack (Block 523). The buffer pointer isreset and the process awaits a next message.

In one embodiment, the CRC is computed using the (AALS) algorithm orsimilar algorithm. The CRC value can be a 32 bit value (e.g., apolynomial specified by section 9.2.1.2 of InternationalTelecommunication Union (ITU) recommendation I.363. The length field canbe 16 bits. The message #/SDU # can be 8 bits. The message #/SDU #values can wrap from 1-255 and a 0 can be a reserved value. In someembodiments, an octet is reserved to pad the metadata to a 32 bitboundary.

FIG. 5B is a flowchart of one embodiment of the receiver finite statemachine for implementing the lighter fragment mechanism. The process ofreceiving NAS or AS data can be initiated in response to receiving datafrom the sender. This received data can be stored in a buffer to beprocessed. In some embodiments, a buffer pointer is used that isinitialized to a starting point (e.g., setting the pointer to position0) (Block 551). The receiver awaits the receipt of fragments from thesender (Block 553). When a middle fragment is received, the payload ofthe fragment is stored in the buffer and the buffer pointer is increasedan amount equivalent to the length of the received fragment (Block 555).The process then continues to await further fragments (Block 553).

When an end fragment is received, the buffer pointer is increased basedon the length of the fragment and the payload is stored in the buffer(Block 557). A check is then made to compare the message/SDU length ofthe received message with an expected message/SDU length as specified inthe message metadata (Block 559). If the message/SDU length is greaterthan the expected message/SDU length, then the receiver sends an errorto the application layer and discards the message. The process thenresets the buffer pointer and awaits a next message (Blocks 551 and553).

If the received message/SDU length is the expected message/SDU length,then the process computes the CRC over the message in the buffer (e.g.,the data in the buffer at the positions between the buffer pointer andthe buffer pointer minus the metadata message/SDU length (Block 561)).If the CRC is not valid, then the message is discarded. The buffer isreset, and the process awaits the next message (Block 551 and 553).

If the CRC is valid, then the message has been validated as beingreassembled correctly and is passed up the stack to the applicationlayer (Block 565). The buffer pointer is reset and the process awaits anext message (Block 551 and 553). In one embodiment, the CRC value canbe a 32 bit value (e.g., a polynomial specified by section 9.2.1.2 ofInternational Telecommunication Union (ITU) recommendation I.363. Thelength field can be 16 bits.

FIG. 5C is a flowchart of one embodiment of a process of an accessgateway function (AGF) to support the lighter fragmentation mechanism.In embodiments where the lighter fragmentation mechanism is implemented,the access gateway function (AGF) or similar application layer functioncan implement handling reliability of AS data by initializing a numberof retries for sending the AS data (e.g., initializing to 3 retries)(Block 571). A message to be sent is then queued to the lighterfragmentation mechanism (Block 573). A timer is then started for themessage (Block 575). The AGF awaits an event related to the messagehandling (Block 577). If an acknowledgement or negative acknowledgementis received, the timer is canceled, and the process completes (Block579). If the timer expires and the number of retries is greater thanzero (Block 581), then the number of retries is decremented (Block 583)and the message is requeued (Block 573).

FIGS. 6A-H are diagrams illustrating a set of cases for the operation ofthe fragmentation mechanism. FIG. 6A is a diagram of the operation ofthe fragmentation mechanism where a message is successfully transferredwithout fragmentation. The sender receives a message that fits within anend fragment payload. The end fragment is generated and sent. Thereceive sends an acknowledgement of the received end fragment. The nextmessage sent is also able to be sent in an end fragment and is similarlyacknowledged.

FIG. 6B is a diagram of the operation of the fragmentation mechanismwhere a set of messages are successfully transferred with fragmentation.The sender receives a first message that is to long for an end fragment.The message is fragmented into two middle fragments and one endfragment. Each fragment is received and the receiver is able to verifyand reassemble the message. The receiver sends an acknowledgement afterthe successful transfer and reassembly. The sender and receiver thenrepeat the process with a next message.

FIG. 6C is a diagram of the operation of the fragmentation mechanismwhere an unfragmented messaged is lost. The sender generates an endfragment for a message that is sent to the receiver. In this case, theend fragment is lost and does not arrive at the receiver. The sender hasa timer that is set when the end fragment is sent. The timer expiresbecause no acknowledgement message is received. In response to the timerexpiration, the message is resent. The resent message arrives correctlyand the receiver sends an acknowledgement.

FIG. 6D is a diagram of the operation of the fragmentation mechanismwhere a fragmented message has a lost middle fragment. In this case, thesender generates two middle fragments and one end fragment to send amessage to the receiver. The second middle fragment is lost. Thereceiver attempts to reassemble the message when the end fragmentarrives. However, the meta data length specified in the end fragmentdoes not match the message length received. The receiver sends anegative acknowledgement to the sender. The sender then resends theentire message with each of the fragments resent. The resent message issuccessfully received and acknowledged.

FIG. 6E is a diagram of the operation of the fragmentation mechanismwhere and end fragment is lost for a fragmented message. In this case, amessage being sent is fragmented into three fragments (two middlefragments and one end fragment). The three fragments are sent but theend fragment is lost. The sender sets a timer when the end fragment issent, which expires due to the loss of the end fragment. After theexpiration of the timer, the three fragments are resent. The resentmessage including each of the three fragments are received and thereceiver successfully validates and acknowledges the receipt of themessage. The metadata length also enables the receiver to determine thefragments that belong to the resent message and to discard the priorreceived fragments.

FIG. 6F is a diagram of the operation of the fragmentation mechanismwhere an acknowledgement of a received message is lost. In this case, amessage is fragmented into three fragments by the sender and each issuccessfully sent to the receiver. The receiver sends anacknowledgement; however, the acknowledgement is lost. This causes atimeout for the sender. As a result, the sender retransmits the entiremessage including each of the three fragments. When the retransmittedfragments are received, the receiver determines that they are duplicatesdue to their message number being the same as the last message. Themessage is not re-processed, but an acknowledgment is sent.

FIG. 6G is a diagram of the operation of the fragmentation mechanismwhere a negative acknowledgement is lost. In this case, a message isfragmented into three fragments and sent to the receiver. One of themiddle fragments is lost. As a result, the receiver sends a negativeacknowledgement, because the metadata length does not match the actualreceived message length. The negative acknowledgement is lost. Thiscauses the sender to have a timeout and consequently resend the entiremessage. The retransmitted message is successfully received and thefragments from the negatively acknowledged message are discarded.

FIG. 6H is a diagram of the operation of the fragmentation mechanismwhere multiple fragments are lost. In this case, message is fragmentedinto three fragments. The end fragment is lost during a firsttransmission of the message. This causes a timeout at the sender, whichthen resends the entire message. In the retransmission, a middlefragment is lost. The receiver attempts to reassemble the message uponreceiving the end fragment of the retransmission. However, the CRC checkwill fail due to the mixture of prior fragments and retransmittedfragments that will be in the receive buffer. A negative acknowledgementis sent and all the fragments discarded at the receiver. In a secondretransmission, the three fragments are successfully transferred andreassembled. The receiver sends an acknowledgment.

FIG. 7A illustrates connectivity between network devices (NDs) within anexemplary network, as well as three exemplary implementations of theNDs, according to some embodiments of the invention. FIG. 7A shows NDs700A-H, and their connectivity by way of lines between 700A-700B,700B-700C, 700C-700D, 700D-700E, 700E-700F, 700F-700G, and 700A-700G, aswell as between 700H and each of 700A, 700C, 700D, and 700G. These NDsare physical devices, and the connectivity between these NDs can bewireless or wired (often referred to as a link). An additional lineextending from NDs 700A, 700E, and 700F illustrates that these NDs actas ingress and egress points for the network (and thus, these NDs aresometimes referred to as edge NDs; while the other NDs may be calledcore NDs).

Two of the exemplary ND implementations in FIG. 7A are: 1) aspecial-purpose network device 702 that uses custom application-specificintegrated-circuits (ASICs) and a special-purpose operating system (OS);and 2) a general purpose network device 704 that uses commonoff-the-shelf (COTS) processors and a standard OS.

The special-purpose network device 702 includes networking hardware 710comprising a set of one or more processor(s) 712, forwarding resource(s)714 (which typically include one or more ASICs and/or networkprocessors), and physical network interfaces (NIs) 716 (through whichnetwork connections are made, such as those shown by the connectivitybetween NDs 700A-H), as well as non-transitory machine readable storagemedia 718 having stored therein networking software 720. Duringoperation, the networking software 720 may be executed by the networkinghardware 710 to instantiate a set of one or more networking softwareinstance(s) 722. Each of the networking software instance(s) 722, andthat part of the networking hardware 710 that executes that networksoftware instance (be it hardware dedicated to that networking softwareinstance and/or time slices of hardware temporally shared by thatnetworking software instance with others of the networking softwareinstance(s) 722), form a separate virtual network element 730A-R. Eachof the virtual network element(s) (VNEs) 730A-R includes a controlcommunication and configuration module 732A-R (sometimes referred to asa local control module or control communication module) and forwardingtable(s) 734A-R, such that a given virtual network element (e.g., 730A)includes the control communication and configuration module (e.g.,732A), a set of one or more forwarding table(s) (e.g., 734A), and thatportion of the networking hardware 710 that executes the virtual networkelement (e.g., 730A).

The networking software 720 can include the fragmentation mechanism 765as described herein. The fragmentation mechanism 765 can be implementedas part of networking software 720 or as a separate set of functions.The fragmentation mechanism 765 can include both the sender and receiverfunctions or the functions of the sender and receiver can be separate.

The special-purpose network device 702 is often physically and/orlogically considered to include: 1) a ND control plane 724 (sometimesreferred to as a control plane) comprising the processor(s) 712 thatexecute the control communication and configuration module(s) 732A-R;and 2) a ND forwarding plane 726 (sometimes referred to as a forwardingplane, a data plane, or a media plane) comprising the forwardingresource(s) 714 that utilize the forwarding table(s) 734A-R and thephysical NIs 716. By way of example, where the ND is a router (or isimplementing routing functionality), the ND control plane 724 (theprocessor(s) 712 executing the control communication and configurationmodule(s) 732A-R) is typically responsible for participating incontrolling how data (e.g., packets) is to be routed (e.g., the next hopfor the data and the outgoing physical NI for that data) and storingthat routing information in the forwarding table(s) 734A-R, and the NDforwarding plane 726 is responsible for receiving that data on thephysical NIs 716 and forwarding that data out the appropriate ones ofthe physical NIs 716 based on the forwarding table(s) 734A-R.

FIG. 7B illustrates an exemplary way to implement the special-purposenetwork device 702 according to some embodiments of the invention. FIG.7B shows a special-purpose network device including cards 738 (typicallyhot pluggable). While in some embodiments the cards 738 are of two types(one or more that operate as the ND forwarding plane 726 (sometimescalled line cards), and one or more that operate to implement the NDcontrol plane 724 (sometimes called control cards)), alternativeembodiments may combine functionality onto a single card and/or includeadditional card types (e.g., one additional type of card is called aservice card, resource card, or multi-application card). A service cardcan provide specialized processing (e.g., Layer 4 to Layer 7 services(e.g., firewall, Internet Protocol Security (IPsec), Secure SocketsLayer (SSL)/Transport Layer Security (TLS), Intrusion Detection System(IDS), peer-to-peer (P2P), Voice over IP (VoIP) Session BorderController, Mobile Wireless Gateways (Gateway General Packet RadioService (GPRS) Support Node (GGSN), Evolved Packet Core (EPC) Gateway)).By way of example, a service card may be used to terminate IPsec tunnelsand execute the attendant authentication and encryption algorithms.These cards are coupled together through one or more interconnectmechanisms illustrated as backplane 736 (e.g., a first full meshcoupling the line cards and a second full mesh coupling all of thecards).

Returning to FIG. 7A, the general purpose network device 704 includeshardware 740 comprising a set of one or more processor(s) 742 (which areoften COTS processors) and physical NIs 746, as well as non-transitorymachine readable storage media 748 having stored therein software 750.During operation, the processor(s) 742 execute the software 750 toinstantiate one or more sets of one or more applications 764A-R. Whileone embodiment does not implement virtualization, alternativeembodiments may use different forms of virtualization. For example, inone such alternative embodiment the virtualization layer 754 representsthe kernel of an operating system (or a shim executing on a baseoperating system) that allows for the creation of multiple instances762A-R called software containers that may each be used to execute one(or more) of the sets of applications 764A-R; where the multiplesoftware containers (also called virtualization engines, virtual privateservers, or jails) are user spaces (typically a virtual memory space)that are separate from each other and separate from the kernel space inwhich the operating system is run; and where the set of applicationsrunning in a given user space, unless explicitly allowed, cannot accessthe memory of the other processes. In another such alternativeembodiment the virtualization layer 754 represents a hypervisor(sometimes referred to as a virtual machine monitor (VMM)) or ahypervisor executing on top of a host operating system, and each of thesets of applications 764A-R is run on top of a guest operating systemwithin an instance 762A-R called a virtual machine (which may in somecases be considered a tightly isolated form of software container) thatis run on top of the hypervisor—the guest operating system andapplication may not know they are running on a virtual machine asopposed to running on a “bare metal” host electronic device, or throughpara-virtualization the operating system and/or application may be awareof the presence of virtualization for optimization purposes. In yetother alternative embodiments, one, some or all of the applications areimplemented as unikernel(s), which can be generated by compilingdirectly with an application only a limited set of libraries (e.g., froma library operating system (LibOS) including drivers/libraries of OSservices) that provide the particular OS services needed by theapplication. As a unikernel can be implemented to run directly onhardware 740, directly on a hypervisor (in which case the unikernel issometimes described as running within a LibOS virtual machine), or in asoftware container, embodiments can be implemented fully with unikernelsrunning directly on a hypervisor represented by virtualization layer754, unikernels running within software containers represented byinstances 762A-R, or as a combination of unikernels and theabove-described techniques (e.g., unikernels and virtual machines bothrun directly on a hypervisor, unikernels and sets of applications thatare run in different software containers).

The software 750 can include the fragmentation mechanism 765 asdescribed herein. The fragmentation mechanism 765 can be implemented aspart of software 750 or as a separate set of functions. Thefragmentation mechanism 765 can include both the sender and receiverfunctions or the functions of the sender and receiver can be separate.

The instantiation of the one or more sets of one or more applications764A-R, as well as virtualization if implemented, are collectivelyreferred to as software instance(s) 752. Each set of applications764A-R, corresponding virtualization construct (e.g., instance 762A-R)if implemented, and that part of the hardware 740 that executes them (beit hardware dedicated to that execution and/or time slices of hardwaretemporally shared), forms a separate virtual network element(s) 760A-R.

The virtual network element(s) 760A-R perform similar functionality tothe virtual network element(s) 730A-R—e.g., similar to the controlcommunication and configuration module(s) 732A and forwarding table(s)734A (this virtualization of the hardware 740 is sometimes referred toas network function virtualization (NFV)). Thus, NFV may be used toconsolidate many network equipment types onto industry standard highvolume server hardware, physical switches, and physical storage, whichcould be located in Data centers, NDs, and customer premise equipment(CPE). While embodiments of the invention are illustrated with eachinstance 762A-R corresponding to one VNE 760A-R, alternative embodimentsmay implement this correspondence at a finer level granularity (e.g.,line card virtual machines virtualize line cards, control card virtualmachine virtualize control cards, etc.); it should be understood thatthe techniques described herein with reference to a correspondence ofinstances 762A-R to VNEs also apply to embodiments where such a finerlevel of granularity and/or unikernels are used.

In certain embodiments, the virtualization layer 754 includes a virtualswitch that provides similar forwarding services as a physical Ethernetswitch. Specifically, this virtual switch forwards traffic betweeninstances 762A-R and the physical NI(s) 746, as well as optionallybetween the instances 762A-R; in addition, this virtual switch mayenforce network isolation between the VNEs 760A-R that by policy are notpermitted to communicate with each other (e.g., by honoring virtuallocal area networks (VLANs)).

The third exemplary ND implementation in FIG. 7A is a hybrid networkdevice 706, which includes both custom ASICs/special-purpose OS and COTSprocessors/standard OS in a single ND or a single card within an ND. Incertain embodiments of such a hybrid network device, a platform VM(i.e., a VM that that implements the functionality of thespecial-purpose network device 702) could provide forpara-virtualization to the networking hardware present in the hybridnetwork device 706.

Regardless of the above exemplary implementations of an ND, when asingle one of multiple VNEs implemented by an ND is being considered(e.g., only one of the VNEs is part of a given virtual network) or whereonly a single VNE is currently being implemented by an ND, the shortenedterm network element (NE) is sometimes used to refer to that VNE. Alsoin all of the above exemplary implementations, each of the VNEs (e.g.,VNE(s) 730A-R, VNEs 760A-R, and those in the hybrid network device 706)receives data on the physical NIs (e.g., 716, 746) and forwards thatdata out the appropriate ones of the physical NIs (e.g., 716, 746). Forexample, a VNE implementing IP router functionality forwards IP packetson the basis of some of the IP header information in the IP packet;where IP header information includes source IP address, destination IPaddress, source port, destination port (where “source port” and“destination port” refer herein to protocol ports, as opposed tophysical ports of a ND), transport protocol (e.g., user datagramprotocol (UDP), Transmission Control Protocol (TCP), and differentiatedservices code point (DSCP) values.

FIG. 7C illustrates various exemplary ways in which VNEs may be coupledaccording to some embodiments of the invention. FIG. 7C shows VNEs770A.1-770A.P (and optionally VNEs 770A.Q-770A.R) implemented in ND 700Aand VNE 770H.1 in ND 700H. In FIG. 7C, VNEs 770A.1-P are separate fromeach other in the sense that they can receive packets from outside ND700A and forward packets outside of ND 700A; VNE 770A.1 is coupled withVNE 770H.1, and thus they communicate packets between their respectiveNDs; VNE 770A.2-770A.3 may optionally forward packets between themselveswithout forwarding them outside of the ND 700A; and VNE 770A.P mayoptionally be the first in a chain of VNEs that includes VNE 770A.Qfollowed by VNE 770A.R (this is sometimes referred to as dynamic servicechaining, where each of the VNEs in the series of VNEs provides adifferent service—e.g., one or more layer 4-7 network services). WhileFIG. 7C illustrates various exemplary relationships between the VNEs,alternative embodiments may support other relationships (e.g.,more/fewer VNEs, more/fewer dynamic service chains, multiple differentdynamic service chains with some common VNEs and some different VNEs).

The NDs of FIG. 7A, for example, may form part of the Internet or aprivate network; and other electronic devices (not shown; such as enduser devices including workstations, laptops, netbooks, tablets, palmtops, mobile phones, smartphones, phablets, multimedia phones, VoiceOver Internet Protocol (VOIP) phones, terminals, portable media players,GPS units, wearable devices, gaming systems, set-top boxes, Internetenabled household appliances) may be coupled to the network (directly orthrough other networks such as access networks) to communicate over thenetwork (e.g., the Internet or virtual private networks (VPNs) overlaidon (e.g., tunneled through) the Internet) with each other (directly orthrough servers) and/or access content and/or services. Such contentand/or services are typically provided by one or more servers (notshown) belonging to a service/content provider or one or more end userdevices (not shown) participating in a peer-to-peer (P2P) service, andmay include, for example, public webpages (e.g., free content, storefronts, search services), private webpages (e.g., username/passwordaccessed webpages providing email services), and/or corporate networksover VPNs. For instance, end user devices may be coupled (e.g., throughcustomer premise equipment coupled to an access network (wired orwirelessly)) to edge NDs, which are coupled (e.g., through one or morecore NDs) to other edge NDs, which are coupled to electronic devicesacting as servers. However, through compute and storage virtualization,one or more of the electronic devices operating as the NDs in FIG. 7Amay also host one or more such servers (e.g., in the case of the generalpurpose network device 704, one or more of the software instances 762A-Rmay operate as servers; the same would be true for the hybrid networkdevice 706; in the case of the special-purpose network device 702, oneor more such servers could also be run on a virtualization layerexecuted by the processor(s) 712); in which case the servers are said tobe co-located with the VNEs of that ND.

A virtual network is a logical abstraction of a physical network (suchas that in FIG. 7A) that provides network services (e.g., L2 and/or L3services). A virtual network can be implemented as an overlay network(sometimes referred to as a network virtualization overlay) thatprovides network services (e.g., layer 2 (L2, data link layer) and/orlayer 3 (L3, network layer) services) over an underlay network (e.g., anL3 network, such as an Internet Protocol (IP) network that uses tunnels(e.g., generic routing encapsulation (GRE), layer 2 tunneling protocol(L2TP), IPSec) to create the overlay network).

A network virtualization edge (NVE) sits at the edge of the underlaynetwork and participates in implementing the network virtualization; thenetwork-facing side of the NVE uses the underlay network to tunnelframes to and from other NVEs; the outward-facing side of the NVE sendsand receives data to and from systems outside the network. A virtualnetwork instance (VNI) is a specific instance of a virtual network on aNVE (e.g., a NE/VNE on an ND, a part of a NE/VNE on a ND where thatNE/VNE is divided into multiple VNEs through emulation); one or moreVNIs can be instantiated on an NVE (e.g., as different VNEs on an ND). Avirtual access point (VAP) is a logical connection point on the NVE forconnecting external systems to a virtual network; a VAP can be physicalor virtual ports identified through logical interface identifiers (e.g.,a VLAN ID).

Examples of network services include: 1) an Ethernet LAN emulationservice (an Ethernet-based multipoint service similar to an InternetEngineering Task Force (IETF) Multiprotocol Label Switching (MPLS) orEthernet VPN (EVPN) service) in which external systems areinterconnected across the network by a LAN environment over the underlaynetwork (e.g., an NVE provides separate L2 VNIs (virtual switchinginstances) for different such virtual networks, and L3 (e.g., IP/MPLS)tunneling encapsulation across the underlay network); and 2) avirtualized IP forwarding service (similar to IETF IP VPN (e.g., BorderGateway Protocol (BGP)/MPLS IPVPN) from a service definitionperspective) in which external systems are interconnected across thenetwork by an L3 environment over the underlay network (e.g., an NVEprovides separate L3 VNIs (forwarding and routing instances) fordifferent such virtual networks, and L3 (e.g., IP/MPLS) tunnelingencapsulation across the underlay network)). Network services may alsoinclude quality of service capabilities (e.g., traffic classificationmarking, traffic conditioning and scheduling), security capabilities(e.g., filters to protect customer premises from network—originatedattacks, to avoid malformed route announcements), and managementcapabilities (e.g., full detection and processing).

FIG. 7D illustrates a network with a single network element on each ofthe NDs of FIG. 7A, and within this straight forward approach contrastsa traditional distributed approach (commonly used by traditionalrouters) with a centralized approach for maintaining reachability andforwarding information (also called network control), according to someembodiments of the invention. Specifically, FIG. 7D illustrates networkelements (NEs) 770A-H with the same connectivity as the NDs 700A-H ofFIG. 7A.

FIG. 7D illustrates that the distributed approach 772 distributesresponsibility for generating the reachability and forwardinginformation across the NEs 770A-H; in other words, the process ofneighbor discovery and topology discovery is distributed.

For example, where the special-purpose network device 702 is used, thecontrol communication and configuration module(s) 732A-R of the NDcontrol plane 724 typically include a reachability and forwardinginformation module to implement one or more routing protocols (e.g., anexterior gateway protocol such as Border Gateway Protocol (BGP),Interior Gateway Protocol(s) (IGP) (e.g., Open Shortest Path First(OSPF), Intermediate System to Intermediate System (IS-IS), RoutingInformation Protocol (RIP), Label Distribution Protocol (LDP), ResourceReservation Protocol (RSVP) (including RSVP-Traffic Engineering (TE):Extensions to RSVP for LSP Tunnels and Generalized Multi-Protocol LabelSwitching (GMPLS) Signaling RSVP-TE)) that communicate with other NEs toexchange routes, and then selects those routes based on one or morerouting metrics. Thus, the NEs 770A-H (e.g., the processor(s) 712executing the control communication and configuration module(s) 732A-R)perform their responsibility for participating in controlling how data(e.g., packets) is to be routed (e.g., the next hop for the data and theoutgoing physical NI for that data) by distributively determining thereachability within the network and calculating their respectiveforwarding information. Routes and adjacencies are stored in one or morerouting structures (e.g., Routing Information Base (RIB), LabelInformation Base (LIB), one or more adjacency structures) on the NDcontrol plane 724. The ND control plane 724 programs the ND forwardingplane 726 with information (e.g., adjacency and route information) basedon the routing structure(s). For example, the ND control plane 724programs the adjacency and route information into one or more forwardingtable(s) 734A-R (e.g., Forwarding Information Base (FIB), LabelForwarding Information Base (LFIB), and one or more adjacencystructures) on the ND forwarding plane 726. For layer 2 forwarding, theND can store one or more bridging tables that are used to forward databased on the layer 2 information in that data. While the above exampleuses the special-purpose network device 702, the same distributedapproach 772 can be implemented on the general purpose network device704 and the hybrid network device 706.

FIG. 7D illustrates that a centralized approach 774 (also known assoftware defined networking (SDN)) that decouples the system that makesdecisions about where traffic is sent from the underlying systems thatforwards traffic to the selected destination. The illustratedcentralized approach 774 has the responsibility for the generation ofreachability and forwarding information in a centralized control plane776 (sometimes referred to as a SDN control module, controller, networkcontroller, OpenFlow controller, SDN controller, control plane node,network virtualization authority, or management control entity), andthus the process of neighbor discovery and topology discovery iscentralized. The centralized control plane 776 has a south boundinterface 782 with a data plane 780 (sometime referred to theinfrastructure layer, network forwarding plane, or forwarding plane(which should not be confused with a ND forwarding plane)) that includesthe NEs 770A-H (sometimes referred to as switches, forwarding elements,data plane elements, or nodes). The centralized control plane 776includes a network controller 778, which includes a centralizedreachability and forwarding information module 779 that determines thereachability within the network and distributes the forwardinginformation to the NEs 770A-H of the data plane 780 over the south boundinterface 782 (which may use the OpenFlow protocol). Thus, the networkintelligence is centralized in the centralized control plane 776executing on electronic devices that are typically separate from theNDs.

The network controller 778, applications 788, or similar control planecomponents can include the fragmentation mechanism 781 as describedherein. The fragmentation mechanism 781 can be implemented as part ofnetwork controller 778 or as a separate set of functions. Thefragmentation mechanism 765 can include both the sender and receiverfunctions or the functions of the sender and receiver can be separate.

For example, where the special-purpose network device 702 is used in thedata plane 780, each of the control communication and configurationmodule(s) 732A-R of the ND control plane 724 typically include a controlagent that provides the VNE side of the south bound interface 782. Inthis case, the ND control plane 724 (the processor(s) 712 executing thecontrol communication and configuration module(s) 732A-R) performs itsresponsibility for participating in controlling how data (e.g., packets)is to be routed (e.g., the next hop for the data and the outgoingphysical NI for that data) through the control agent communicating withthe centralized control plane 776 to receive the forwarding information(and in some cases, the reachability information) from the centralizedreachability and forwarding information module 779 (it should beunderstood that in some embodiments of the invention, the controlcommunication and configuration module(s) 732A-R, in addition tocommunicating with the centralized control plane 776, may also play somerole in determining reachability and/or calculating forwardinginformation—albeit less so than in the case of a distributed approach;such embodiments are generally considered to fall under the centralizedapproach 774, but may also be considered a hybrid approach).

While the above example uses the special-purpose network device 702, thesame centralized approach 774 can be implemented with the generalpurpose network device 704 (e.g., each of the VNE 760A-R performs itsresponsibility for controlling how data (e.g., packets) is to be routed(e.g., the next hop for the data and the outgoing physical NI for thatdata) by communicating with the centralized control plane 776 to receivethe forwarding information (and in some cases, the reachabilityinformation) from the centralized reachability and forwardinginformation module 779; it should be understood that in some embodimentsof the invention, the VNEs 760A-R, in addition to communicating with thecentralized control plane 776, may also play some role in determiningreachability and/or calculating forwarding information—albeit less sothan in the case of a distributed approach) and the hybrid networkdevice 706. In fact, the use of SDN techniques can enhance the NFVtechniques typically used in the general purpose network device 704 orhybrid network device 706 implementations as NFV is able to support SDNby providing an infrastructure upon which the SDN software can be run,and NFV and SDN both aim to make use of commodity server hardware andphysical switches.

FIG. 7D also shows that the centralized control plane 776 has a northbound interface 784 to an application layer 786, in which residesapplication(s) 788. The centralized control plane 776 has the ability toform virtual networks 792 (sometimes referred to as a logical forwardingplane, network services, or overlay networks (with the NEs 770A-H of thedata plane 780 being the underlay network)) for the application(s) 788.Thus, the centralized control plane 776 maintains a global view of allNDs and configured NEs/VNEs, and it maps the virtual networks to theunderlying NDs efficiently (including maintaining these mappings as thephysical network changes either through hardware (ND, link, or NDcomponent) failure, addition, or removal).

While FIG. 7D shows the distributed approach 772 separate from thecentralized approach 774, the effort of network control may bedistributed differently or the two combined in certain embodiments ofthe invention. For example: 1) embodiments may generally use thecentralized approach (SDN) 774, but have certain functions delegated tothe NEs (e.g., the distributed approach may be used to implement one ormore of fault monitoring, performance monitoring, protection switching,and primitives for neighbor and/or topology discovery); or 2)embodiments of the invention may perform neighbor discovery and topologydiscovery via both the centralized control plane and the distributedprotocols, and the results compared to raise exceptions where they donot agree. Such embodiments are generally considered to fall under thecentralized approach 774, but may also be considered a hybrid approach.

While FIG. 7D illustrates the simple case where each of the NDs 700A-Himplements a single NE 770A-H, it should be understood that the networkcontrol approaches described with reference to FIG. 7D also work fornetworks where one or more of the NDs 700A-H implement multiple VNEs(e.g., VNEs 730A-R, VNEs 760A-R, those in the hybrid network device706). Alternatively or in addition, the network controller 778 may alsoemulate the implementation of multiple VNEs in a single ND.Specifically, instead of (or in addition to) implementing multiple VNEsin a single ND, the network controller 778 may present theimplementation of a VNE/NE in a single ND as multiple VNEs in thevirtual networks 792 (all in the same one of the virtual network(s) 792,each in different ones of the virtual network(s) 792, or somecombination). For example, the network controller 778 may cause an ND toimplement a single VNE (a NE) in the underlay network, and thenlogically divide up the resources of that NE within the centralizedcontrol plane 776 to present different VNEs in the virtual network(s)792 (where these different VNEs in the overlay networks are sharing theresources of the single VNE/NE implementation on the ND in the underlaynetwork).

On the other hand, FIGS. 7E and 7F respectively illustrate exemplaryabstractions of NEs and VNEs that the network controller 778 may presentas part of different ones of the virtual networks 792. FIG. 7Eillustrates the simple case of where each of the NDs 700A-H implements asingle NE 770A-H (see FIG. 7D), but the centralized control plane 776has abstracted multiple of the NEs in different NDs (the NEs 770A-C andG-H) into (to represent) a single NE 7701 in one of the virtualnetwork(s) 792 of FIG. 7D, according to some embodiments of theinvention. FIG. 7E shows that in this virtual network, the NE 7701 iscoupled to NE 770D and 770F, which are both still coupled to NE 770E.

FIG. 7F illustrates a case where multiple VNEs (VNE 770A.1 and VNE770H.1) are implemented on different NDs (ND 700A and ND 700H) and arecoupled to each other, and where the centralized control plane 776 hasabstracted these multiple VNEs such that they appear as a single VNE770T within one of the virtual networks 792 of FIG. 7D, according tosome embodiments of the invention. Thus, the abstraction of a NE or VNEcan span multiple NDs.

While some embodiments of the invention implement the centralizedcontrol plane 776 as a single entity (e.g., a single instance ofsoftware running on a single electronic device), alternative embodimentsmay spread the functionality across multiple entities for redundancyand/or scalability purposes (e.g., multiple instances of softwarerunning on different electronic devices).

Similar to the network device implementations, the electronic device(s)running the centralized control plane 776, and thus the networkcontroller 778 including the centralized reachability and forwardinginformation module 779, may be implemented a variety of ways (e.g., aspecial purpose device, a general-purpose (e.g., COTS) device, or hybriddevice). These electronic device(s) would similarly includeprocessor(s), a set or one or more physical NIs, and a non-transitorymachine-readable storage medium having stored thereon the centralizedcontrol plane software. For instance, FIG. 8 illustrates, a generalpurpose control plane device 804 including hardware 840 comprising a setof one or more processor(s) 842 (which are often COTS processors) andphysical NIs 846, as well as non-transitory machine readable storagemedia 848 having stored therein centralized control plane (CCP) software850.

The non-transitory machine readable medium 848 can include thefragmentation mechanism 881 as described herein. The fragmentationmechanism 765 can be implemented as part of network controller instance878 or as a separate set of functions. The fragmentation mechanism 881can include both the sender and receiver functions or the functions ofthe sender and receiver can be separate.

In embodiments that use compute virtualization, the processor(s) 842typically execute software to instantiate a virtualization layer 854(e.g., in one embodiment the virtualization layer 854 represents thekernel of an operating system (or a shim executing on a base operatingsystem) that allows for the creation of multiple instances 862A-R calledsoftware containers (representing separate user spaces and also calledvirtualization engines, virtual private servers, or jails) that may eachbe used to execute a set of one or more applications; in anotherembodiment the virtualization layer 854 represents a hypervisor(sometimes referred to as a virtual machine monitor (VMM)) or ahypervisor executing on top of a host operating system, and anapplication is run on top of a guest operating system within an instance862A-R called a virtual machine (which in some cases may be considered atightly isolated form of software container) that is run by thehypervisor; in another embodiment, an application is implemented as aunikernel, which can be generated by compiling directly with anapplication only a limited set of libraries (e.g., from a libraryoperating system (LibOS) including drivers/libraries of OS services)that provide the particular OS services needed by the application, andthe unikernel can run directly on hardware 840, directly on a hypervisorrepresented by virtualization layer 854 (in which case the unikernel issometimes described as running within a LibOS virtual machine), or in asoftware container represented by one of instances 862A-R). Again, inembodiments where compute virtualization is used, during operation aninstance of the CCP software 850 (illustrated as CCP instance 876A) isexecuted (e.g., within the instance 862A) on the virtualization layer854. In embodiments where compute virtualization is not used, the CCPinstance 876A is executed, as a unikernel or on top of a host operatingsystem, on the “bare metal” general purpose control plane device 804.The instantiation of the CCP instance 876A, as well as thevirtualization layer 854 and instances 862A-R if implemented, arecollectively referred to as software instance(s) 852.

In some embodiments, the CCP instance 876A includes a network controllerinstance 878. The network controller instance 878 includes a centralizedreachability and forwarding information module instance 879 (which is amiddleware layer providing the context of the network controller 778 tothe operating system and communicating with the various NEs), and an CCPapplication layer 880 (sometimes referred to as an application layer)over the middleware layer (providing the intelligence required forvarious network operations such as protocols, network situationalawareness, and user—interfaces). At a more abstract level, this CCPapplication layer 880 within the centralized control plane 776 workswith virtual network view(s) (logical view(s) of the network) and themiddleware layer provides the conversion from the virtual networks tothe physical view.

The centralized control plane 776 transmits relevant messages to thedata plane 780 based on CCP application layer 880 calculations andmiddleware layer mapping for each flow. A flow may be defined as a setof packets whose headers match a given pattern of bits; in this sense,traditional IP forwarding is also flow-based forwarding where the flowsare defined by the destination IP address for example; however, in otherimplementations, the given pattern of bits used for a flow definitionmay include more fields (e.g., 10 or more) in the packet headers.Different NDs/NEs/VNEs of the data plane 780 may receive differentmessages, and thus different forwarding information. The data plane 780processes these messages and programs the appropriate flow informationand corresponding actions in the forwarding tables (sometime referred toas flow tables) of the appropriate NE/VNEs, and then the NEs/VNEs mapincoming packets to flows represented in the forwarding tables andforward packets based on the matches in the forwarding tables.

Standards such as OpenFlow define the protocols used for the messages,as well as a model for processing the packets. The model for processingpackets includes header parsing, packet classification, and makingforwarding decisions. Header parsing describes how to interpret a packetbased upon a well-known set of protocols. Some protocol fields are usedto build a match structure (or key) that will be used in packetclassification (e.g., a first key field could be a source media accesscontrol (MAC) address, and a second key field could be a destination MACaddress).

Packet classification involves executing a lookup in memory to classifythe packet by determining which entry (also referred to as a forwardingtable entry or flow entry) in the forwarding tables best matches thepacket based upon the match structure, or key, of the forwarding tableentries. It is possible that many flows represented in the forwardingtable entries can correspond/match to a packet; in this case the systemis typically configured to determine one forwarding table entry from themany according to a defined scheme (e.g., selecting a first forwardingtable entry that is matched). Forwarding table entries include both aspecific set of match criteria (a set of values or wildcards, or anindication of what portions of a packet should be compared to aparticular value/values/wildcards, as defined by the matchingcapabilities—for specific fields in the packet header, or for some otherpacket content), and a set of one or more actions for the data plane totake on receiving a matching packet. For example, an action may be topush a header onto the packet, for the packet using a particular port,flood the packet, or simply drop the packet. Thus, a forwarding tableentry for IPv4/IPv6 packets with a particular transmission controlprotocol (TCP) destination port could contain an action specifying thatthese packets should be dropped.

Making forwarding decisions and performing actions occurs, based uponthe forwarding table entry identified during packet classification, byexecuting the set of actions identified in the matched forwarding tableentry on the packet.

However, when an unknown packet (for example, a “missed packet” or a“match-miss” as used in OpenFlow parlance) arrives at the data plane780, the packet (or a subset of the packet header and content) istypically forwarded to the centralized control plane 776. Thecentralized control plane 776 will then program forwarding table entriesinto the data plane 780 to accommodate packets belonging to the flow ofthe unknown packet. Once a specific forwarding table entry has beenprogrammed into the data plane 780 by the centralized control plane 776,the next packet with matching credentials will match that forwardingtable entry and take the set of actions associated with that matchedentry.

A virtual circuit (VC), synonymous with virtual connection and virtualchannel, is a connection oriented communication service that isdelivered by means of packet mode communication. Virtual circuitcommunication resembles circuit switching, since both are connectionoriented, meaning that in both cases data is delivered in correct order,and signaling overhead is required during a connection establishmentphase. Virtual circuits may exist at different layers. For example, atlayer 4, a connection oriented transport layer datalink protocol such asTransmission Control Protocol (TCP) may rely on a connectionless packetswitching network layer protocol such as IP, where different packets maybe routed over different paths, and thus be delivered out of order.Where a reliable virtual circuit is established with TCP on top of theunderlying unreliable and connectionless IP protocol, the virtualcircuit is identified by the source and destination network socketaddress pair, i.e. the sender and receiver IP address and port number.However, a virtual circuit is possible since TCP includes segmentnumbering and reordering on the receiver side to prevent out-of-orderdelivery. Virtual circuits are also possible at Layer 3 (network layer)and Layer 2 (datalink layer); such virtual circuit protocols are basedon connection oriented packet switching, meaning that data is alwaysdelivered along the same network path, i.e. through the same NEs/VNEs.In such protocols, the packets are not routed individually and completeaddressing information is not provided in the header of each datapacket; only a small virtual channel identifier (VCI) is required ineach packet; and routing information is transferred to the NEs/VNEsduring the connection establishment phase; switching only involveslooking up the virtual channel identifier in a table rather thananalyzing a complete address. Examples of network layer and datalinklayer virtual circuit protocols, where data always is delivered over thesame path: X.25, where the VC is identified by a virtual channelidentifier (VCI); Frame relay, where the VC is identified by a VCI;Asynchronous Transfer Mode (ATM), where the circuit is identified by avirtual path identifier (VPI) and virtual channel identifier (VCI) pair;General Packet Radio Service (GPRS); and Multiprotocol label switching(MPLS), which can be used for IP over virtual circuits (Each circuit isidentified by a label).

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

1. A method to implement a fragmentation mechanism for a session betweena 5G-residential gateway (5G-RG) and access gateway function (AGF)communicating over point to point protocol over Ethernet (PPPoE) thatencapsulates control messages, where the 5G-RG or the AGF is a sender ofa message, the method comprising: receiving the message to be sent thatdoes not fit within a maximum transmission unit for the session;generating a first fragment of the message and a second fragment of themessage; and sending the first fragment of the message and the secondfragment of the message to a receiver, the second fragment includingmetadata with a length of the message, and a cyclic redundancy check. 2.The method of claim 1, further comprising: starting a timer in responseto sending the second fragment.
 3. The method of claim 2, furthercomprising: resending the first fragment and the second fragment inresponse to the timer expiring.
 4. The method of claim 2, furthercomprising: cancelling the timer in response to receiving anacknowledgement from the receiver.
 5. The method of claim 2, furthercomprising: generating a communication error in response to the timerexpiring or a negative acknowledgement and a number of retries beingexhausted.
 6. A method to implement a fragmentation mechanism for asession between a 5G-residential gateway (5G-RG) and access gatewayfunction (AGF) communicating over point to point protocol over Ethernet(PPPoE) that encapsulates control message, where the 5G-RG or the AGF isa receiver of a message, the method comprising: receiving a firstfragment and a second fragment of the message from a sender; determiningwhether the second fragment is an end fragment, the end fragmentincluding metadata with a length of the message, and a cyclic redundancycheck; checking the length against the first fragment and the secondfragment; validating the cyclic redundancy check; and extracting themessage from the first fragment and second fragment in response to thelength and the cyclic redundancy check being correct.
 7. The method ofclaim 6, further comprising: sending an acknowledgement to the sender,in response to a message number, the length, and the cyclic redundancycheck being correct.
 8. The method of claim 6, further comprising:sending a negative acknowledgement or discarding the message, inresponse to the length not correlating with the first fragment and thesecond fragment or the cyclic redundancy check failing.
 9. The method ofclaim 6, further comprising: sending an acknowledgement and discarding aduplicate message, in response to a message number matching a priormessage number.
 10. The method of claim 6, wherein the message is anaccess stratum (AS) or non-access stratum (NAS) message.
 11. A computingdevice to implement a method of a fragmentation mechanism for a sessionbetween a 5G-residential gateway (5G-RG) and access gateway function(AGF) communicating over point to point protocol over Ethernet (PPPoE)that encapsulates control messages, where the 5G-RG or the AGF is asender of a message, the computing device comprising: a non-transitorymachine readable medium having stored therein the fragmentationmechanism; and a processor coupled to the non-transitory machinereadable medium, the processor to execute the fragmentation mechanism,the fragmentation mechanism to receive the message to be sent that doesnot fit within a maximum transmission unit for the session, to generatea first fragment of the message and a second fragment of the message,and to send the first fragment of the message and the second fragment ofthe message to a receiver, the second fragment including a metadata witha length of the message, and a cyclic redundancy check.
 12. Thecomputing device of claim 11, wherein the fragmentation mechanism isfurther to start a timer in response to sending the second fragment. 13.The computing device of claim 12, wherein the fragmentation mechanism isfurther to resend the first fragment and the second fragment in responseto the timer expiring.
 14. The computing device of claim 12, wherein thefragmentation mechanism is further to cancel the timer in response toreceiving an acknowledgement from the receiver.
 15. The computing deviceof claim 12, wherein the fragmentation mechanism is further to generatea communication error in response to the timer expiring or a negativeacknowledgement and a number of retries being exhausted.
 16. A computingdevice to implement a method of a fragmentation mechanism for a sessionbetween a 5G-residential gateway (5G-RG) and access gateway function(AGF) communicating over point to point protocol over Ethernet (PPPoE)that encapsulates control messages, where the 5G-RG or the AGF is areceiver of a message, the computing device comprising: a non-transitorymachine readable medium having stored therein the fragmentationmechanism; and a processor coupled to the non-transitory machinereadable medium, the processor to execute the fragmentation mechanism,the fragmentation mechanism to receive a first fragment and a secondfragment of the message from a sender, determine whether the secondfragment is an end fragment, the end fragment including metadata with alength, and a cyclic redundancy check, to check the length against thefirst fragment and second fragment, to validate the cyclic redundancycheck, and to extract the message from the first fragment and secondfragment, in response to the length, and the cyclic redundancy checkbeing correct.
 17. The computing device of claim 16, wherein thefragmentation mechanism is further to send an acknowledgement to thesender, in response to a message number, the length, and the cyclicredundancy check being correct.
 18. The computing device of claim 16,wherein the fragmentation mechanism is further to send a negativeacknowledgement or discarding the message, in response to the length notcorrelating with the first fragment and the second fragment.
 19. Thecomputing device of claim 16, wherein the fragmentation mechanism isfurther to send an acknowledgement and discarding a duplicate message,in response to a message number matching a prior message number.
 20. Thecomputing device of claim 16, wherein the message is an access stratum(AS) or non-access stratum (NAS) message.